The present invention relates to a rotary rolling piston compressor with fixed vane, and more specifically to a new construction for the sliding slot of the vane of this type of compressor.
In rotary rolling piston type compressors the fixed sliding vane causes the separation of two chambers in the interior of the cylinder into a suction chamber at low pressure and a compression chamber at high pressure. This separation is obtained as the vane tip follows the rolling piston movement under the bias of a spring. Due to the fact of separating two chambers with great pressure difference, the vane is forced against the surface of the slot in which it slides by the high pressure in the compression chamber. This causes problems concerning contact of metallic parts and wear between the sliding van and the slot.
One of the well-known solutions attempts to reduce this problem through the improvement of the vane lubrication system, especially in the place where the contact of metallic parts occurs. This is the case of the U.S. Pat. No. 4,629,403 (TECUMSEH). Another effort is to reduce the difference of pressure between the chambers at the end of the compression cycle according to U.S. Pat. No. 4,664,608 (G.E.).
Although these solutions reduce the wear between the vane and the slot, they cause losses in the volumetric efficiency of the compressor.
On the first mentioned solution (U.S. Pat. No. 4,629,403), the placement of a lubricating hole with oil at high pressure connected to the suction, or low pressure, chamber through the clearance for the sliding of the vane at the slot, causes leakage of this oil to the interior of the cylinder during the compression cycle. This increases the temperature of the refrigerant fluid in the suction chamber, reducing its volumetric efficiency.
On this first solution the aim is to reduce the vane and the slot wear through the lubricating provision on the places where the wear of the parts occurs. However, in spite of reducing the problem of vane and slot wear, this first solution requires a flow of the lubricating oil to a value that becomes detrimental to the compressor efficiency because it results in an undesirable heating of the refrigerant fluid held within the suction volume of the cylinder.
On the second solution (U.S. Pat. No. 4,664,608) the opening of the hole for the pressure release will always occur at a certain rotation angle of the crankshaft, whether the discharge pressure has been reached in the cylinder or not. This depends on the operational conditions in which the compressor is used. This may cause backflow of the refrigerant gas already discharged within the shell to the interior of the cylinder, which obviously adversely affects the energy and volumetric efficiency of the compressor.